This invention relates to toners, developers containing toners, processes thereof, and methods for generating developed images with, for example, offset-like print quality. More specifically, in embodiments thereof the present invention relates to toners and developers with, for example, controlled properties that provide offset-like print quality when used in developing electrostatic images with, for example, a device containing a hybrid scavengeless development system, and wherein calcium stearate is selected as a toner additive.
The toners and developers of the present invention can be selected for a number of electrophotographic marking processes including color processes. One type of color electrophotographic marking process, referred to as image-on-image (IOI) processing, superimposes toner powder images of different color toners onto the photoreceptor prior to the transfer of the composite toner powder image onto the substrate. While the IOI process provides a number of benefits, such as a compact architecture, there can be several challenges to its successful implementation. For instance, the viability of printing system concepts, such as IOI processing, can require development systems that do not interact substantially with a previously toned image. Since several known development systems, such as conventional magnetic brush development and jumping single-component development, interact with the image on the receiver, a previously toned image will be scavenged by subsequent development if interacting development systems are used. Thus, for the IOI process, there is a need for scavengeless or noninteractive development systems, and which need is achievable with the toners and developers of the present invention.
Hybrid scavengeless development (HSD) technology develops toner via a conventional magnetic brush onto the surface of a donor roll. A plurality of electrode wires is closely spaced from the toned donor roll in the development zone. An AC voltage is applied to the wires to generate a toner cloud in the development zone. This donor roll generally comprises a conductive core covered with a thin, for example about 50 to about 200 μm, partially conductive layer. The magnetic brush roll is held at an electrical potential difference relative to the donor core to produce the field necessary for toner development. The toner layer on the donor roll is then disturbed by electric fields from a wire or set of wires to produce and sustain an agitated cloud of toner particles. Typical AC voltages of the wires relative to the donor are about 700 to about 900 Vpp at frequencies of about 5 to about 15 kHz. These AC signals are often square waves, rather than pure sinusoidal waves. Toner from the cloud is then developed onto the nearby photoreceptor by fields created by a latent image. In the present invention in embodiments, while any suitable electrostatic image development device may be used, it is preferred to use a device employing the hybrid scavengeless development system, such as the system illustrated herein, and, for example, U.S. Pat. No. 5,978,633, the disclosure of which is totally incorporated herein by reference.
The achievement of stringent offset-like print quality requirements in a xerographic engine has been enabled in the present invention by IOI xerography of which hybrid scavengeless development is an excellent subsystem component. Both the image quality and the unique subsystem requirements result in highly constrained toner designs of which the toners of the present invention are useful. In addition to achieving offset-like print quality, a digital imaging processes enables customization of each print (such as an address, or special information for regional distribution), which is not as practical with offset lithography.